Between 2001-2003 there were 11.6 million annual ambulatory care visits for skin and soft tissue infections, with a 31% increase in emergency department visits compared to the previous decade, according to the National Hospital AmbulatoryMedical Care Survey data. The majority of these infections are caused by community-associated methicillin resistant Staphylococcus aureus (CA-MRSA) and most CA-MRSA infections are manifested as skin and soft tissue infections. As the prevalence of CA-MRSA continues to increase worldwide each year, with community outbreaks observed in multiple settings, it is not surprising that more and more hospitals are being affected by this surge in patient visits. Pediatric and general emergency departments are often the first line for diagnosis and treatment of these infections which may include a painful drainage procedure. A history and physical examination by a health care provider has thus far been the standard of care in diagnosing skin and soft tissue infections. At times inaccurate, the clinical exam can lead to misdiagnosing (either over or underestimating) a lesion that requires drainage. Emergency ultrasound (EUS) is a commonly used tool in general emergency departments for various diagnosis and treatments including the diagnosis of drainable soft tissue infections. The utility of EUS as an adjunct to the clinical examination in pediatric patients for soft tissue infections is unknown. The primary objective of this study is to determine and compare the sensitivity and specificity of clinical examination alone with that of the exam plus EUS in children. This will be done through a cross-sectional study design conducted in a large, urban, tertiary-care pediatric emergency department. Children with suggestion of soft tissue infection will be prospectively enrolled. Physicians are trained in bedside emergency ultrasound for evaluation of soft tissue infections prior to patient enrollment. The reference standard is the presence of a soft tissue infection requiring drainage defined as purulent material expressed if a drainage procedure is performed, or if no drainage is performed, the need for a drainage procedure or spontaneous drainage within two days of the initial visit. Sample size calculations are based upon a hypothesized change in sensitivity of at least 9% with the addition of EUS. Statistical analysis will include calculation of test characteristics, conditional logistic regression with model building, and derivation of ROC curves. PUBLIC HEALTH RELEVANCE: The rise in visits for soft tissue infections is an important public health issue today. Emergency bedside ultrasound in children may offer improvement in the diagnosis of these infections, and therefore, ultimately may result in more rapid and appropriate treatment, with improved patient outcomes.